1. Field of the Invention
The present invention relates to a storage system and data management method and, for instance, is preferably employed in a storage system.
2. Description of the Related Art
Conventionally, as a management method of stored data in a storage system, the process of backing up data stored in a volume and, when there is any failure in this volume (including the data stored in this volume), using this backup data for rebuilding the volume to the state prior to such failure is being widely used.
As this kind of backup method in a storage system, conventionally, there is a method where, when data is written in a primary volume from a host computer, a so-called journal representing the written content (data itself or an address with data written therein, etc.) is transferred from the primary side to the secondary side, and the same data is written in a secondary volume in the same address according to this journal on the secondary side. According to this method, a volume having the entirely same contents as the primary volume can be created on the secondary side.
Further, as a rebuilding method of a volume in a storage system, a method has been proposed for enabling the rebuilding of the state of the primary volume at an arbitrary point in time by employing such journal and a snapshot function of the storage system (c.f. Japanese Patent Laid-Open Publication No. 2005-18738). Incidentally, a snapshot is a memory image of the primary volume at a certain point in time.
With this method, in addition to sequentially accumulating journals, a snapshot of the primary volume is acquired in prescribed time intervals, and, when rebuilding the content of the volume at a certain time (this is hereinafter referred to as the “rebuilding time”), a snapshot having an acquisition time that is earlier than the rebuilding time and in which the acquisition time thereof is closest to the rebuilding time is sequentially subject to the journals, in the order from old to new, from the time such snapshot was acquired up to the rebuilding time. Further, foregoing Japanese Patent Laid-Open Publication No. 2005-18738 discloses that first and second threshold limits are provided to the cumulative amount of the journals, and, by controlling the cumulative amount of the journals to constantly be within the first and second threshold limits, overload of the memory capacity caused by unnecessary journals can be prevented.
Moreover, as a backup and volume rebuilding processing method, disclosed is a method of providing to the secondary side a volume for storing the same contents as the primary volume via remote copying and a volume for retaining backup data of the primary volume at a certain point in time, and, when rebuilding the primary volume, foremost, the volume retaining the secondary backup data is copied to the other volume on the secondary side, and this volume is thereafter copied to the primary volume (c.f. Japanese Patent Laid-Open Publication No. 2003-233518).